Hi Christy,

What's the version of your Outlook 2016?
Outlook 2016 (16.0.5197.1000) MSO 32-bit

I will plan on running a manual update. Thank you.

Yes, the issue was just reported recently. No special action that I have seen in the history of this machine.

As far as I know, when searching in the Outlook client, we need to change the search scope to get the correct search results, such as the Current Folder, All Mailboxes, etc. If you set up a search in the current folder, then messages in other folders will not be searched. Please check it.

Thank you. I've tried including all folders, etc. Checked for items that should have retrieved results, to no avail. I had also gone through these steps listed in the link.

I will plan re-installation of Office.

Thanks,
Rudy

Hi Patrick. I did come across your links while I was googling the errors. That in itself did not really address my issues. Seems like it was a brief spike.
I'll review further if the issue manifests again.
Thanks for the suggestion, however. I'll mark as an accepted answer.

Hello. I apologize for the delayed response. I'm being very cautious since this is a process I have not performed before. I realized also that I may have submitted the incorrect cert details. The correct one is listed below. Is there anything that I should be concerned about - breaking something else in this process? Anything I should be especially careful about, since there are other certs in current active use? Is the process still the same as that for the certificate I originally submitted for?

[77985-certificate-exchange-ucc-2017.txt][1]![79098-certlist.png][2]![79099-cert1.png][3]![79161-cert2.jpg][4]![79162-cert3.jpg][5]

Hello again, Jeff.

There is no DAG environment in place here, and there is a single Exchange server.

We did recently have to restore a mailbox. We had to mount a database temporarily. That has since been removed. But these Events coincide with that activity. I imagine there is some residue.

I've checked for any mailbox moves or exports. None exist. Those request were deleted when I first embarked on investigation of this issue.

Regards,
Rudy

Hi Jeff - the issue has not manifested any further. For now, I'll just archive this case and investigate further if the issue retuns.

Thank you for your input.

Regards,
Rudy

Thank you both for your responses. Very helpful.
I presume that using Microsoft Edge in I.E mode will also not work, correct?
Thanks in advance.

Hi Jeff - Thank you and Yuki for the suggestions. It is an odd issue. I'll work on troubleshooting using the feedback I've received from you and Yuki.

I'll close this case for now.

Regards,
Rudy

Thank you for the feedback.

The way you are indicating is exactly how we currently have it setup. However, attempts to email the the "external email address" for some of these "mail users", senders have received NDR's. I'm not sure why. I've attached an example NDR.

Trying again...
115211-ndr.pdf

Thank you for your assistance and input, YukiSun.
I will follow through with the recommendations and see how things go.
I think we can close this case for now. I'll create a new case again if needed.

Regards,
Rudy

Here's the AD item I'm talking about.

Thank you everyone for the feedback. I apologize for the delayed update. I have narrowed down the source of the problem.

I found that this issue was manifesting for multiple external email addresses.

I looked at the Outlook Properties for the Auto-Fill entry. I found that there were additional details including an entry for the Department. I then found that there was an Active Directory account for this external user. I found that these people log on to our Active Directory in order to access some applications. However, they do not use our email system, having their own organizational email. This external email address was defined in the Active Directory account. They do not have a mailbox on our Exchange server.

Even after deleting the Auto-Fill entry, when the new email address was typed in the To: field, it would populate using this Active Directory account.

Taking the following action appears to have addressed the issue.

1. Removed external email address A.D.
   

2. Updated Address Book.
   

3. Deleted the Auto-Fill entry.

In some cases, it appeared that this was not sufficient. For these, I added a Contact configured for the external email address. I also created a local mailbox with the local email address. Then, forwarded email to the Contact.

1. Should an Active Directory account NOT include an external email address if it is being used solely for reference? We also add these users' phone number, for instance.
   

2. What then is the Microsoft best pracice in situations like this?

Thanks again.

Regards,
Rudy

Thank you both. I am going through the pre-checks. I ran the commands to confirm which is being used. The output doesn't have any matching certs. Am I missing something?

We proceed with a paid case with Microsoft. I may have a possible solution. I'll poste once verified.

Hello - I'm checking a possible solution, and will update once confirmed.